Field of the Invention
Embodiments of the present invention relate generally to a blanking system for multi charged particle beams, and a multi charged particle beam writing apparatus, and more specifically, to a blanking system in multi-beam writing, for example.
Description of Related Art
The lithography technique that advances miniaturization of semiconductor devices is extremely important as a unique process whereby patterns are formed in semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits is decreasing year by year. The electron beam writing technique, which intrinsically has excellent resolution, is used for writing or “drawing” a pattern on a wafer, etc. with electron beams.
As an example employing the electron beam writing technique, a writing apparatus using multiple beams (multi-beams) can be cited. Compared with the case of writing a pattern by using a single electron beam, since it is possible to emit multiple beams at a time in multi-beam writing, the throughput can be greatly increased. For example, in a writing apparatus employing a multi-beam system, multi-beams are formed by letting portions of an electron beam emitted from an electron gun pass through a corresponding hole of a plurality of holes in the mask, each of the beams is blanking-controlled, and each unblocked beam is reduced by an optical system and deflected by a deflector so as to irradiate a desired position on a target object or “sample”.
In multi-beam writing, the dose of each beam is separately controlled based on an irradiation time. For highly accurately controlling such a dose of each beam, it is necessary to perform high speed blanking control to provide an ON or OFF state of each beam. In a writing apparatus of a multi-beam system, a blanking control circuit for each beam is mounted on a blanking aperture array (BAA) where respective blankers for multi-beams are arranged. A control signal is output to the control circuit for each of these beams.
The throughput of a multi-beam writing apparatus is rate controlled determined by data transmission to the blanking aperture array. Conventionally, it is common that signal connection is performed by wire bonding between a blanking aperture array and an mounting substrate on which a blanking aperture array is mounted. However, the wire bonding has a problem in that impedance mismatch may easily occur. This leads to a problem in that it is difficult to perform a clock operation at high speed in data transmission. Furthermore, it is difficult to have a large installation density in order to avoid contact between wires, and therefore, it has no choice but to increase the number of control circuits for individual beams each controlled by one signal line. Therefore, the number of times of clock operation in data transmission required for one shot increases, which causes a problem of becoming an obstacle to increase a data transmission rate.
As a technique relevant to a blanking system, there is disclosed a technique in which a plurality of blankers (electrodes) are connected in parallel to one circuit where a shift register and a switch are arranged, and a plurality of circuits each having this structure are connected in order to one data line, so as to perform data transmission (e.g., refer to Japanese Patent No. 3394237).